Garrett D'Amore wrote:
One potential concern. I know of certain bits of code where strings
like "$Id: some text$" are "edited" in place to form version numbers
from $Id$ and similar strings.
The places I can think of actually occur in kernel code!
I suspect that making this the default _might_ break a number of
things. It would be very, very helpful if we had compiler help to
_detect_ incorrect attempts to write to constant strings. I'm not sure
-xstrconst will give us the warnings to catch them before they become
bugs in the field.
Sorry, no -xstrconst won't give you any such warnings. If we could
figure out how to give that warning, we'd give it w/o using -xstrconst :-)
Douglas
-- Garrett
Roland Mainz wrote:
Adam Leventhal wrote:
On Tue, Mar 06, 2007 at 04:37:59PM +0100, [EMAIL PROTECTED] wrote:
Ok. I'll bite... what is a "tail merging string". And does this save
space (as I think the name implies)?
Suppose you have two strings:
Permission Denied.
You're not authorized. Permission Denied.
If the strings can be modified, you need to store both.
Any bets on how much space this will save in the kernel (or anywhere)? My
guess is fewer than 100 bytes.
I think this is more in the range of megabytes since the kernel is full
of duplicate strings.
Quick look at the problem (kernel only):
-- snip --
# scan all kernel files and dump all strings (or things which look like
strings)
$ cat $(find /kernel /usr/kernel /platform -type f) | strings -a | wc -c
15951405
# scan all kernel files for string-like stuff and remove duplicates
$ cat $(find /kernel /usr/kernel /platform -type f) | strings -a | sort
-u | wc -c
5342818
$ bc -l
(15951405-5342818) / (1024 * 1024)
10.11713695526123046875
-- snip --
In theory we could save ~~10.1MB in the kernel (userland is likely much
worse).
Note that "strings -a" lists lots of garbage which isn't really strings
which means the number will be below 10.1MB. Another limiting factor is
that we cannot fold multiple string literals across module borders but I
guess we can still save 3-5MB minimum.
The number could be improved a little bit by adding a compiler option to
fold all identical+duplicate read-only which will save some more memory.
----
Bye,
Roland
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